Haversine's formula for distance less than 5 meters

I am trying to use haversin formula to prevent mysql table from being updated. I am implementing a reusable based application where data is mac, route, lat, long

written by passbus devices im bus and sent to server.

My database table has mac address as UNIQUE KEY

. So to avoid another passenger on the same bus storing their data in the table, I would filter these queries with Haversin formula

, but I tried it with a tow point that is about 20 meters close together, but I get quantity4803.800129810092

//calculate the distance between the request sender and all other request in the ArrayList. 

  private double haversineDistance(LatLong x, LatLong y) {  
        final int R = 6371; // Radious of the earth
    double xLat = x.getLatitude();
    double xLon = x.getLongitude();
    double yLat = y.getLongitude();
    double yLon = y.getLongitude();
    ;
    double latDistance = toRad(yLat - xLat);
    double lonDistance = toRad(yLon - xLon);
    double a = Math.sin(latDistance / 2) * Math.sin(latDistance / 2)
            + Math.cos(toRad(xLat)) * Math.cos(toRad(yLat))
            * Math.sin(lonDistance / 2) * Math.sin(lonDistance / 2);
    double c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    double distance = R * c;

      System.out.println("The distance between two lat and long is:" + distance);

        return distance;

    }